This invention relates to a press for compressing an absorbent article to squeeze liquid materials from it. More particularly, the invention provides a press for transferring liquid and dissolved materials from one absorbent article to another layered with it. A particular feature of the invention is the provision of such a press that transfers the liquid materials with only minimal lateral spreading. This is desired to avoid loss of liquid materials in the first article and thereby to transfer the utmost volume of materials to the second article, and to concentrate the transferred materials in a confined region of the second article.
A press embodying the invention is particularly useful in connection with the analysis of a biological liquid sample to identify the concentration of one or more constituents. According to one technique for such an analysis as disclosed for example in U.S. Pat. Nos. 3,036,893; 3,216,804; 3,219,416; 3,260,413; 3,261,668; 3,331,665; 3,368,872; and 3,502,438; the sample is deposited on a first absorbent pad and then transferred to a second absorbent pad where, with the addition of chemical reagents, a reaction product is developed in an amount dependent on the concentration of a constituent in the original sample. The above-noted Natelson Patent No. 3,261,668 discloses an elementary flat-bed type of press for squeezing two layered pads together to enhance the transfer of liquid materials between them. However, this prior art press generally transfers only a relatively small portion of the liquid materials in one pad to the other pad; due, at least in part, to the fact that the press spreads the liquid. The press of the Natelson U.S. Pat. No. 3,331,665 operates with disks of the pad material and does not restrict spreading of liquid within the disks.
Also in the prior art are teachings regarding metalworking punch presses, such as is disclosed in Henricson U.S. Pat. No. 1,723,935, which strip the work piece from the punch after the punching operation. U.S. Pat. Nos. 2,160,676; 2,168,377; 2,265,331; 2,268,787; and 2,350,436 disclose further punch presses of this type.